diff --git a/ryu/controller/controller.py b/ryu/controller/controller.py
index 48ab83cc..a18d6668 100644
--- a/ryu/controller/controller.py
+++ b/ryu/controller/controller.py
@@ -58,7 +58,7 @@ class OpenFlowController(object):
 
     # entry point
     def __call__(self):
-        #LOG.debug('call')
+        # LOG.debug('call')
         self.server_loop()
 
     def server_loop(self):
@@ -84,7 +84,7 @@ class OpenFlowController(object):
                                    CONF.ofp_tcp_listen_port),
                                   datapath_connection_factory)
 
-        #LOG.debug('loop')
+        # LOG.debug('loop')
         server.serve_forever()
 
 
@@ -147,7 +147,7 @@ class Datapath(ofproto_protocol.ProtocolDesc):
 
                 msg = ofproto_parser.msg(self,
                                          version, msg_type, msg_len, xid, buf)
-                #LOG.debug('queue msg %s cls %s', msg, msg.__class__)
+                # LOG.debug('queue msg %s cls %s', msg, msg.__class__)
                 if msg:
                     ev = ofp_event.ofp_msg_to_ev(msg)
                     self.ofp_brick.send_event_to_observers(ev, self.state)
diff --git a/ryu/controller/dpset.py b/ryu/controller/dpset.py
index b74e2ec4..399bed93 100644
--- a/ryu/controller/dpset.py
+++ b/ryu/controller/dpset.py
@@ -112,7 +112,7 @@ class DPSet(app_manager.RyuApp):
             self.logger.debug('DPSET: Forgetting datapath %s', self.dps[dp.id])
             self.logger.debug('DPSET: New datapath %s', dp)
         self.dps[dp.id] = dp
-        if not dp.id in self.port_state:
+        if dp.id not in self.port_state:
             self.port_state[dp.id] = PortState()
             ev = EventDP(dp, True)
             for port in dp.ports.values():
@@ -122,7 +122,7 @@ class DPSet(app_manager.RyuApp):
 
     def _unregister(self, dp):
         # see the comment in _register().
-        if not dp in self.dps.values():
+        if dp not in self.dps.values():
             return
         LOG.debug('DPSET: unregister datapath %s', dp)
         assert self.dps[dp.id] == dp